Comminuting device



May 28, 1963 c. H. NORDELL COMMINUTING DEVICE 6 Sheets-Sheet 1 Filed Nov. 9, 1959 w W v W T :12 ii.

6 Sheets-Sheet 3 lvuian/imp C. H. NORDELL COMMINUTING DEVICE May 28, 1963 Filed Nov. 9, 1959 May 28, 1963 c. H. NORDELL 3,091,337

COMMINUTING DEVICE Filed Nov. 9, 1959 6 Sheets-Sheet 4 mg. 6 J 7 70 My 7o May 28, 1963 c. H. NORDELL COMMINUTING DEVICE Filed Nov. 9, 1959 6 Sheets-Sheet 6 106 g gm I, 15

United States Patent Ofi 3,091,337 Patented May 28, 1963 ice 3,091,337 COMMINUTING DEVICE Carl H. Nordell, Crystal Bay, Nev., assignmof fifteen percent each to Louise N. Millspaugh and Anne N. Kaspar, both of Palm Springs, Calif.

Filed Nov. 9, 1959, SerQNo. 851,641 3 Claims. (Cl. 210-173) This invention relates to a comminuting device, and is particularly concerned with means for reciprocating a reversible cutting cylinder along the upstream surface of a screen fixed in a sewage channel to remove solids from said screen, and with a comb adapted to cooperate with said cutting cylinder to comminute solids removed from said screen, regardless of the direction of rotation of said cylinder.

In accordance with the present invention, a screen having vertically disposed screen elements is secured in vertical position transversely of a channel through which the sewage flows. A horizontally disposed cutting cylinder is rotatably mounted in a frame adapted to be moved vertically relative to the screen, and a stationary comb is mounted on the frame in position to cooperate with the teeth of the cutting cylinder regardless of the direction of rotation to comminute solids intercepted by the screen and removed from the screen by the cutting cylinder.

The supporting frame, which carries the cutting cylinder and comb, is reciprocated by a screw operated by the same electric motor that rotates the cutting cylinder. A sleeve secured to the supporting frame moves vertically with it, and carries two spaced projections that engage limit switches at each end of the vertical travel of the cutting cylinder. The limit switches reverse the motor, and thereby reverse the direction of rotation of the cylinder and also reverse the direction of its vertical travel.

The comb comprises a plurality of short comb sections that may be reversed individually when one edge becomes worn. The comb is so positioned that it cooperates with the teeth of the cutting cylinder to comminute the solids carried by the cutting cylinder to the comb, regardless of the direction of rotation or the direction of vertical movement of the cutting cylinder.

If the cutting cylinder engages a log or other solid too large to be comminuted as it is moving upwardly, such solid will fall back into the sewage without damage to the comminuting device. However, if the cutting cylinder engages such an obstruction on its downward movement, the obstruction may get wedged between the cutting cylinder and bottom of the sewage channel. An obstruction resting on the bottom of the channel may prevent the cutting cylinder from moving downwardly far enough to enable the sleeve to engage the limit switch to reverse the motor. Under such conditions the screw continues to rotate, and, since the sleeve cannot move downwardly, the nut in which the screw rotates moves upwardly. A second sleeve connected to the nut moves upwardly with it, and trips alever connected to a rod which operates the limit switch to reverse the motor, and the cutting cylinder starts on its upward movement before any damage can be done to the comminuting device.

The movable frame is provided with ball bearing shoes that ride on a track on the stationary frame in which the screen is secured, to facilitate the vertical movement of the cutting cylinder. The screw which lifts the vertically movable frame is provided with ball bearing engagement with its nut to reduce the friction of said lifting screw to a minimum.

The structure by means of which the above-mentioned and other advantages of the invention are attained will be fully described in the following specification, taken in conjunction with the accompanying drawings showing a '2 preferred illustrative embodiment of the invention, in which:

FIGURE 1 is a front elevational view of a comminuting device embodying the invention, with the'cutting cylinder in its lowermost position;

FIG. 2 is a side elevational view of the comminuting device, looking towards the left side of FIG. 1;

FIG. 3 is a bottom plan view, looking upwardly from the plane 3-3 of FIG. 1;

FIG. 4 is a top plan view, looking downwardly from the plane 44 of FIG. 1;

FIG. 5 is a fragmentary front view on an enlarged scale, partly in section and partly in elevation;

FIG. 6 is a fragmentary side view on an enlarged scale, partly in section and partly in elevation, with the screw for reciprocating the cutting cylinder in its lowermost position;

FIG. 7 is a fragmentary view, similar to FIG. 6, showing the screw in its uppermost position;

FIG. 8 is a fragmentary vertical sectional view on an enlarged scale, showing the ball bearing engagement of the screw and its nut;

FIG. 9 is a fragmentary perspective view on an enlarged scale, showing the engagement of one of the ball bearing shoes with its track for guiding the vertical movement of the cutting cylinder;

FIG. I0 is a vertical sectional view, taken along line '1010 of FIG. 11, showing the ball bearing shoe;

FIG. 11 is a vertical sectional view, taken along the line 11-11 of FIG. 10;

FIG. 12 is a cross sectional view, taken along line 12I2 of FIG. 11;

FIG. 13 is a fragmentary side view, partly in section and partly in elevation, showing the stationary comb adapted to cooperate with the cutting cylinder rotating in either direction;

FIG. 14 is a fragmentary side view, partly in elevation and partly in section, showing the reversing switch and automatic means for operating the switch when a log or similar obstruction prevents downward movement of the cutting cylinder;

FIG. 15 is a fragmentary side elevational view of the comminuting device, with the cutting cylinder moving downwardly; and

FIG. 16 is a fragmentary side view, partly in section and partly in elevation, showing the lever for operating the reversing switch being tripped when an obstruction prevents downward movement of the cutting cylinder.

Referring to the drawings, the reference numeral 2 indicates a sewage channel having a bottom 3 and upstanding side walls 4 and 5. A framefi, comprising a pair of vertically disposed channel members 7, a top channel member 8 and a bottom member 9, is rigidly secured in vertical position transversely of channel 2. A screen 10 is rigidly secured in the lower portion of frame 6. The screen shown is provided with vertically arranged V-shaped bars 11, but any suitable screen elements may be used. A track 12 is mounted vertically adjacent each longitudinal edge of screen 10. A second frame 13 is movably mounted adjacent frame 6 and is provided with shoes 14, hereinafter described, which engage tracks 12 and hold frame 13in proper spaced relationship to frame 6.

Frame 13 comprises side plates 15, 16 and a housing 17 adjacent the inner surface of side plate 16. Aligned bearings 18 project inwardly from the lower ends of side plate v15 and housing 17. A reversible cutting cylinder 19 is rotatably mounted in bearings 18. The cutting cylinder is provided with laterally projecting teeth 2t) adapted to enter the V-shaped spaces in elements 11 as the cut ting cylinder is rotated. Cutting cylinder 19 is also preferably provided with a plurality of shear bars 21 between teeth 20.

Side plates and 16 provide a rigid connection with cutting cylinder 19 and the upper portion of frame 13 so that the cutting cylinder is reciprocated verticaily with the upper portion of frame 13, as hereinafter described. A sprocket 22 fixed to shaft 23 of cutting cylinder 19 is driven by a chain 24 enclosed in a housing 17. Chain 24 extends around sprocket 22 and around a sprocket 25 which drives the chain.

As shown in FIG. 5, the upper portion of frame 13 comprises a spacer 26 and a housing 27 secured to each other in end to end relationship. Spacer 26 is rigidly secured to side plate 15 at its outer end, and housing 27 is rigidly secured at its outer end to housing 17. A reversible electric motor 28 is mounted on the upper side of housing 27 which has an opening 29' through which the output shaft 30 of the motor depends. Motor 28 is energized by wires in a flexible cable 31 connecting it to a junction box 32 mounted on top member 8 of frame 6, as shown in FIG. 1. cable 31 is waterproof, although normally both of these members are above the sewage level in the lowermost position of frame 13.

The lower portion of output shaft 30 is reduced in diameter, as indicated at 33, (FIG. 5), and is provided with a worm drive 34. A bearing 35 mounted in the end of housing 27 adjacent spacer 26 rotatably supports a shaft 36 having a worm wheel 37 fixed thereto. Worm wheel 37 engages worm drive 34 by which it is driven. The outer end of shaft 36 is reduced in diameter, as indicated at 38 and is rotatably mounted in a bearing 39 that is mounted in the outer end of housing 27. The outer end of shaft 36 extends into housing 17, and sprocket 25 is mounted thereon. A bevel pinion gear 40 is mounted on the intermediate portion of shaft 36 for a purpose hereinafter described.

Housing 27 has another opening 41 in its upper side, and a flanged collar 42 depends therethrough into the housing. Two vertically aligned annular bearings 43 that are separated vertically by a spacer 44 are mounted in collar 42. An annular ring 45 fitting over the flange of collar 42 engages the top of upper bearing 43 to hold the bearings and collar 42 against movement relative to housing 27. A screw 46 is rigidly fixed at its lower end to the top of a vertical shaft 47 rotatably mounted in bearings 43. Screw 46 may be integral with shaft 47, if desired. A bevel gear 48, fixed to the bottom of shaft 47, is meshed with pinion gear 40 so that motor 28 simultaneously rotates cutting cylinder 19 on a horizontal axis and screw 46 on a vertical axis.

Screw 46 is enclosed within a sleeve 49 (FIG. 6) fixed at its lower end to a collar 50 and at its upper end to a collar 51. Collar 50 is mounted on top of annular ring 45 and is fixed relative to frame 13. The upper end of screw 46 is threaded into a nut 52 that is located in sleeve 49. Nut 52 is spaced from the inner surface of sleeve 49 by a collar 53 into which its upper end is threaded, as indicated at 54. A lock nut 55 and a washer 56 are secured to the upper end of screw 46 to prevent separation of nut 52 from the screw. A wear band 57 is interposed between the outer surface of collar 53 and the inner surface of sleeve 49 to facilitate sliding movement therebetween.

Frame 13 is moved vertically, relative to frame 6. as screw 46 is rotated. The inner diameter of nut 52 is larger than the diameter of screw 46, as indicated at 58, FIG. 8. Screw 46 and the inner surface of nut 52 are provided with complementary helical grooves 59 and 60, respectively. Ball bearings 61, which are positioned between grooves 59 and 60, are such size that they simultaneously engage screw 46 and nut 52. The threaded engagement between nut 52 and collar 53. indicated at 54, has much greater friction than the ball bearing engagement between screw 46 and nut 52. Accordingly. when screw 46 is rotated, it moves relative to nut 52, while Motor 28 is submersible, and

nut 52 remains fixed relative to collar 53. Since screw 46 is rigidly fixed to the top of vertical shaft 47, which is held against vertical movement relative to frame 13, rotation of the screw moves frame 13 vertically relative to stationary frame 6.

Rotation of screw 46 carries ball bearings 61 upwardly or downwardly along the path defined by grooves 59 and 60, according to the direction of rotation of screw 46 when screw 46 moves vertically relative to nut 52. A return tube 62 extends through nut 52 and is secured in place by any suitable means, such as, for example, a strap 63. The ends of tube 62 engage groove 59 to form a closed path of travel for the ball bearings.

If screw 46 is turned counterclockwise, as viewed in FIG. 8, it moves upwardly, and the uppermost ball hearing 61 is forced into the upper end of return tube 62. Each ball bearing pushes those ahead of it, so as to form a continuous pattern of ball bearings moving into the upper end of tube 62 and out of the lower end of the tube into the grooves 59, 60. When the rotation of screw 46 is reversed, the ball bearings move into the return tube at its lower end and out of it at its upper end. if the vertical movement of screw 46 relative to nut 52 is stopped while the screw is rotating, nut 52 is moved upwardly by the screw and moves collar 53. The significance of such movement will be hereinafter discussed.

As shown in FIG. 6, a second sleeve 64 has its lower end extending below the upper end of screw 46 and into collar 53. Sleeve 64 is supported at its upper end by a block 65. Collar 51 is provided with a pair of vertically spaced annular sealing rings 66 and 67 which engage sleeve 64 to prevent water or contaminating material from getting into sleeve 49. Block 65 is provided with breather openings 76 and 68, as shown in MG. 14, to allow escape or entrance of air from or into sleeves 49 and 64. This air flows through apertures 69 and 69 (FIG. 6).

Block 65 is supported by a bolt 70 which extends through slotted openings 71 in two spaced plates 72 and 73 extending forwardly from top member 8 of frame 6. Plates 72 and 73 are integral with a base plate 74 bolted to top member 8, as indicated at 75 in P16. 14. Slotted openings 71 also permit a slight upward movement of sleeve 64, under certain conditions, hereinafter described.

As motor 28 rotates screw 46 to move frame 13 upwardly, it also rotates cutting cylinder 19 to cause teeth 20 on the bottom side of the cylinder to move upwardly into the V-shaped spaces in screen elements 11, and then forwardly away from the screen. Teeth 20 transfer solids from the screen into engagement with a comb 77 that is stationary relative to frame 13. Cutting cylinder 19 and comb 77 are mounted in frame 13. The solids intercepted by the screen from the sewage flowing through channel 2 are transferred from the screen to the comb by the teeth of the cutting cylinder during the vertical movement of the cutting cylinder in both directions.

Comb 77 is adapted to cooperate with teeth 20 of the cutting cylinder to comminute the solids that are forced through notches 78 (FIG. 3) in the comb. The length of comb 77 is approximately equal to the length of the cutting cylinder, and the comb is arranged to cooperate with all the teeth of the cutting cylinder. As shown in FIG. 13, comb 77 is mounted in fixed position in a plane that is radially disposed relative to the longitudinal axis of cutting cylinder 19. This arrangement of the comb causes the forward edge of each tooth 20 to engage the comb at (approximately) right angles as it enters notch 78, with which it is aligned. The cutting angle between the forward edge of each tooth 20 and comb 77 is the same regardless of the direction of rotation of the teeth. The specific angular engagement of the forward edge of each tooth 20 with the comb makes it possible for the comb and the cutting cylinder to comminute the solids continuously during the rotation of the cutting cylinder in either direction.

The specific position of the comb relative to the periphcry of the cutting cylinder may be varied with certain limits, but the specific angular relationship between the forward edges of teeth 20 and the comb must be maintained to obtain efficient cornminution of the solids with a single stationary comb during the vertical movement of the cutting cylinder in each direction. The comb is on the side of the longitudinal center of the cutting cylinder opposite the screen, and preferably its plane is spaced not more than thirty degrees from the plane perpendicular to thefaoeof the screen.

Comb 77 may comprise a single bar of a length approximately equal to the length of cutting cylinder 19, but preferably comprises a plurality of short comb sections 79 having notches 78 along the edge thereof. The comb sections are secured to a suitable supporting mem ber, such as, forexample, a casing 80, by screws or bolts 81, as shown in FIG. 3. The holes in the comb sections through which bolts 81 extend are preferably slightly larger than the diameter of the bolt to provide clearance, and to. permit small lateral adjustments of the comb sections relative to the frame to insure accurate alignment of notches 78 with teeth 20 of cutting cylinder 19.

Notches 78 may be provided along only one edge of comb 77, but preferably are provided along opposite edges thereof. The provision of notches on opposite edges ofxthe comb sections permits reversal of any comb section that becomes worn, to present a new comb edge to the teeth of cutting cylinder 19. When the second edge of any comb section becomes worn, it is necessary to replace only a'single comb section 79, instead of replacing the entire comb.

in order to facilitate assembly of the comb, comb sections 79 are preferably grouped together in units of two or more, as shown in FIG. 3. Each group of comb sections is secured to a bar 82 by bolts 83 or any other securing means that permit easy removal of individualcomb sections, as shown in FIG. 3. Small gaps 84 are provided between'adjacent ends of bars 82, so that the bars will not interfere with the small lateral adjustment permitted by the clearance between the bolt holes in the comb sections and the bolts passing therethrough.

If'desired, a unit of two or more comb sections may be reversed without removing any comb section from bar 82 when one or more of the comb sections becomes worn. When a second comb section in any unit becomes worn it is necessary to remove at least one of the worn sections from bar 82. The worn section may be reversed to provide a new comb edge. If both edges of a comb section become worn, it is necessary to replace only the worn section.

Casting 80 is supported in fixed position by extensions 85 that project forwardly from side plate and housing 17, as shown in FIG. 13. The extensions are preferably integral with side plate 15 and housing 17, but may be formed as separate members and secured to said parts in any suitable manner. The casting may be of any desired shape, and is provided with a flat surface 86 against which comb 77 is secured.

In the embodiment illustrated in the drawings, fiat surface 86 compris s one face of a recess in casting 80. The flat surface is disposed in a plane that is radially disposed to the longitudinal axis of cutting cylinder 19. Comb 77, secured to the flat surface by bolts 81, projects rearwardly from the rear edge of the casting a distance sufficient to allow teeth of cutting cylinder 19 to pass through notches 78 as'the cutting cylinder is rotated. A plate 87 secured to casting 80 by bolts 88, has one edge abutting the underside of comb 77 opposite the rear edge of the casting to provide additional support for the comb.

During the vertical movement of frame 13 relative to frame 6, the proper spaced relationship between the frames is maintained by the engagement of shoes 14 with track 12. One track 12 is secured adjacent one edge of a vertical channel 7 by a plate 89 that extends vertically at right angles to one leg of channel 7. At the opposite side of the machine, the other track 12 is supported in one corner of a vertical angle member 90 adjacent the outer edge of channel 7. The difference between the means for supporting track 12 at opposite sides of the machine is necessary because housing 17 extends outwardly to the outer edge of channel 7 at the second side. Track 12 must be located beyond the outer edge of housing 17. In addition to maintaining a predetermined spaced relationship between frames 6 and 13, the engagement of shoes 14 and track 12 reduces the friction between these frames to a minimum as frame 13 is moved vertically relative to frame 6.

Referring to FIGS. 9 to 12 of the drawings, a boss 91, integral with side wall 15 or 16 and projecting outwardly from said side wall, is provided with threaded bores 92. Each shoe 14 is mounted on a boss 91 by means of screws 94 which extend through the shoe and are threaded into bores 92.

Each shoe comprises an inner race 97, an outer race 98, and a plurality of ball bearings 99 between said inner and outer races. A screw 96 extending through both races is threaded into a spacer which confines the ball bearings between said races. Spacer 95 is positioned against boss 91 to which it is secured by screws 94. Boss '91 is so located on side plate 1 5 or 16 that when the structure is assembled, ball bearings 99 along the rear longitudinal edge of shoe I4 engage track 12. Outer race 98 is provided with a flange 100 that extends around its entire perimeter except at its rear longitudinal edge. T he rear edge of outer race 98 is curved inwardly a short distance, as indicated at 101, FIG. 10, which is snfiicient to retain the ban bearings in the shoe without interfering with their engagement with track 12.

A reversing switch 102 mounted on one verticai channel member 7 is provided with a lever 103, pivoted as indicated at 104, FIG. 14, to operate the switch. An upper bracket 105 and a lower bracket 106 are rigidly secured to sleeve 49 in vertically spaced relationship so that one is above switch 102 and the other is below it. Each of brackets 105 and 106 has a portion projecting from sleeve 49 far enough to engage lever 103. When frame 13 reaches the predetermined upper limit of its upward movement, bracket 106 trips lever 103 and operates switch 102 to reverse motor 28, thereby reversing the direction of rotation of cutting cylinder 19 and simultaneousely starting the downward movement of frame 13. When the lowermost limit is reached, bracket 105 trips lever 103 to operate the switch, thereby reversing the direction of rotation of cutting cylinder 19 and starting the upward movement of frame 13.

If an obstruction, such as a log 107 (FIG. 15) that cannot be comminuted easily, becomes wedged between teeth 20 and bottom 3 of channel 2 as frame 13 is moving downwardly, it may stop the downward movement of frame 13 before bracket 105' reaches a lever 103. Motor 28 will continue operating in the same direction and will continue to rotate screw 46. Since screw 46 and sleeve 49 are rigidly connected to frame 13 they are also held against downward movement. Continued operation of motor 28 therefore causes nut 52 to move upwardly relative to screw 46. The upward movement of nut 52 moves collar '53 upwardly, and the collar carries sleeve 64 upwardly with it.

A lever 108, pivoted to plate 73, as indicated at 109, has one end in engagement with block 65, as shown in FIGS. 14 and 16. Block 65 is moved upwardly by sleeve 64 to move lever 108 about its pivot 109 as soon a the downward movement of screw 46 is stopped. A rod 110 is secured to lever 108 on the opposite side of pivot 109 and is moved downwardly when the end of lever 188 engaged by block 65 is tilted upwardly. Rod 110 extends through aligned apertures 111 and 112 in plate 74 and top channel 8, respectively, and is guided thereby in its downward movement. The lower end of rod 110 is positioned above lever 103 in close proximity thereto. The tilting movement of lever 108 is sufficient to cause rod 110 to trip lever 103 to operate switch 102 and thereby reverse motor 28. Reversal of motor 28 starts frame 13 on its upward movement from the point where the downward movement thereof was stopped. As cutting cylinder 19 moves upwardly obstruction 107 may be removed from the screen, and frame 13 may continue its normal travel thereafter.

The combined weight of frame 13, cutting cylinder 19, housing 27, motor 28, and sleeve 49, all of which move vertically as a single unit, exerts considerable force on lift screw 46 during such vertical movement, particularly when the center of gravity is spaced a considerable distance from the axis of the screw. The eccentric load causes excessive moments of force against the ball bearing screw lift, and thereby increases the wear and shortens the life of the ball bearing screw lift.

The eccentric load also interferes with proper positioning of the frame and cutting cylinder relative to the screen. When the cutting cylinder strikes a solid too large to comminute in one pass it bites out a portion of the solid and swings outwardly from the screen, as described in Lannert Patent No. 2,900,082. When the cutting cylinder swings back after passing such a solid, unequal distribution of weight may cause the frame to cock and thus prevent the cutting cylinder from returning to its proper position.

If the weight is not distributed properly to position the center of gravity in proximity to the axis of ball bearing lift screw 46 a counter weight 113 may be added, to reduce the moments of force against the ball bearing screw lift, and to insure proper positioning of the cutting cylinder when it swings back into position after passing a solid that forces it away from the screen.

counterweight 113 may be of any desired shape, but preferably fits substantially within the thickness of channel member 7. As shown, one end of the counterweight is provided with flanges 114 to engage the outer edges of channel member 7 to guide the counterweight in its vertical movement. The counterweight must be short enough to prevent its lower edge from engaging the upper edge of screen 10 when the counterweight is in its lowermost position. The counterweight is provided adjacent its opposite edge with a vertical bore 115 through which a guide rod 116 extends. The upper end of guide rod 116 is secured to top channel member 8, and its lower end is secured to an angle iron 117 (FIG. 2) extending transversely across frame 6.

The counterweight is secured to one end of a cable 118 that runs over a pulley 119 mounted on top of channel member 8. The opposite end of cable 118 is connected to spacer 26 and is positioned to counterbalance the eccentric load added to frame 13 by cutting cylinder 19, housing 27, motor 28, and sleeve 49, and to position the center of gravity in proximity to the axis of the ball bearing screw lift to ease the vertical movement of frame 13 and its associated structure. The ball bearing screw lift works best under some load, and it is preferred to counterbalance approximately 75% of the combined weight of the frame and associated structure, thereby leaving about 25% of the load on the ball bearing lift screw to prevent slippage of the ball bearings and to retain control of the vertical movement of frame 13.

In the normal operation of the comminuting device constructed in accordance with the present invention, the cutting cylinder travels continuously between the upper and lower edges of the screen, reversing its direction of vertical travel and its direction of rotation each time it reaches either the upper or lower edge of the screen. The teeth of the cutting cylinder transfer the solids intercepted by the screen from the screen to a single comb. The comb is stationary with respect to the frame that carries it and the cutting cylinder vertically along the upstream surface of the screen. The angle of the comb relative to the teeth of the cutting cylinder is such that the solids are comminuted by the interaction of the teeth and the comb in both directions of movement of the cutting cylinder.

It is impossible for any obstruction encountered by the cutting cylinder to jam or break the machine. The teeth on the upper half of the cutting cylinder rotate away from the screen as the cutting cylinder moves upwardly, so that obstructions encountered on the upward movement are pushed away from the screen. Normally any obstruction encountered on the downward movement of the cutting cylinder is also pushed from the screen by the teeth. However, if the obstruction gets caught between the cylinder and the bottom of the channel the limit of vertical travel of the cutting cylinder is shortened until the obstruction is removed.

Although I have described a preferred embodiment of the invention in considerable detail, it will be understood that the description is intended to be illustrative, rather than restrictive, as many details may be modified or changed without departing from the spirit or scope of the invention. Accordingly, I do not desire to be restricted to the exact structure described.

I claim:

1. A sewage comminuting device comprising a stationary screen, a frame reciprocably mounted adjacent said screen and adapted to traverse said screen, a reversible cutting cylinder rotatably mounted in said frame for removing sewage solids from said screen, means for causing said frame to traverse said screen, means for continuously rotating said cutting cylinder alternately in each of two opposite directions, cutting teeth having two oppositely disposed cutting edges mounted on said cutting cylinder and engageable with one surface of said screen, a single thin fiat comb immovably mounted on said frame and having a forward surface adjacent said cutting cylinder, said comb having a rearward surface as well, said comb lying along a plane in which the longitudinal axis of said cutting cylinder lies, which plane also intersects the rearward and forward surfaces of said comb, notches of uniform cross section in the forward surface throughout their depth in said comb, said notches having oppositely disposed cutting edges, said teeth being adapted to mesh with the notches of said comb when said cylinder is rotated in either direction, the edges of said notches and the edges of said cutting teeth being disposed to cooperate to comminute sewage solids as said cutting cylinder rotates alternately in each of said two opposite directions, switch means operable to reverse the direction of movement of said frame, and means carried by said frame to operate said switch means at predetermined points in the travel of said frame in each direction to reverse the direction of travel of said frame and the direction of rotation of said cutting cylinder.

2. The device of claim 1 in which said frame reciprocates upwardly and downwardly with respect to said screen and in which automatic means are provided to reverse the direction of travel of said frame when the downward movement of said frame is stopped in advance of one of said predetermined points in the travel of said frame.

3. The device of claim 1 wherein there is provided a stationary frame to which the stationary screen is connected and wherein said automatic means include a rod adapted to engage said switch means, said rod being normally positioned in spaced relationship to said switch means, and means operated by said means for causing said moveable frame to traverse said screen to move said rod into operating engagement with said switch means when the downward movement of said moveable frame is stopped in advance of one of said predetermined points in the travel of said moveable frame.

(References on following page) References Cited in the file of this patent UNITED STATES PATENTS Montgomery Aug. 22, 1939 Thom Dec. 22, 1942 Geyer et a1 May 26, 1953 Lauwasser May 10, 1955 10 Lannert July 28, 1959 Lannert Aug. 18, 1959 LZlf at a] June 6, 1961 FOREIGN PATENTS Germany Nov. 8, 1928 UNITED STATES PATENT OFFICE CERTIFICATE OF CORRECTION Patent No. 3,091,337 May 28, 1963 Carl H. Nordell It is hereby certified that error appears in the above numbered patent requiring correction and that the said Letters Patent should read as correc ted below Column 5, line 15, for "easing" read casting column 8, line 63, for the claim reference numberal "1" read 2 Signed and sealed this 3rd day of December 1963.

(SEAL) EEI I IEST W SWIDER EDWIN L. REYNOLDS Attesting Officer Ac ting Commissioner of Patents 

1. A SEWAGE COMMUNITING DEVICE COMPRISING A STATIONARY SCREEN, A FRAME RECIPROCABLY MOUNTED ADJACENT SAID SCREEN AND ADAPTED TO TRAVERSE SAID SCREEN, A REVERSIBLE CUTTING CYLINDER ROTATABLY MOUNTED IN SAID FRAME FOR REMOVING SEWAGE SOLIDS FROM SAID SCREEN, MEANS FOR CAUSING SAID FRAME TO TRAVERSE SAID SCREEN, MEANS FOR CONTINUOUSLY ROTATING SAID CUTTING CYLINDER ALTERNATELY IN EACH OF TWO OPPOSITE DIRECTIONS, CUTTING TEETH HAVING TWO OPPOSITELY DISPOSED CUTTING EDGES MOUNTED ON SAID CUTTING CYLINDER AND ENGAGEABLE WITH ONE SURFACE OF SAID SCREEN, A SINGLE THIN FLAT COMB IMMOVABLY MOUNTED ON SAID FRAME AND HAVIANG A FORWARD SURFACE ADJACENT SAID CUTTING CYLINDER, SAID COMB HAVING A REARWARD SURFACE AS WELL, SAID COMB LYING ALONG A PLANE IN WHICH THE LONGITUDINAL AXIS OF SAID CUTTING CYLINDER LIES, WHICH PLANE ALSO INTERSECTS THE REARWARD AND FORWARD SURFACES OF SAID COMB, NOTCHES OF UNIFORM CROSS SECTION IN THE FORWARD SURFACE THROUGHOUT THEIR DEPTH IN SAID COMB, SAID NOTCHES HAVING OPPOSITELY DISPOSED CUTTING EDGES, SAID TEETH BEING ADAPTED TO MESH WITH THE NOTCHES OF SAID COMB WHEN SAID CYLINDER IS ROTATED IN EITHER DIRECTION, THE EDGES OF SAID NOTCHES AND THE EDGES OF SAID CUTTING TEETH BEING DISPOSED TO COOPERATE TO COMMINUTE SEWAGE SOLIDS AS SAID CUTTING CYLINDER ROTATES ALTERNATELY IN EACH OF SAID TWO OPPOSITE DIRECTIONS, SWITCH MEANS OPERABLE TO REVERSE THE DIRECTION OF MOVEMENT OF SAID FRAME, AND MEANS CARRIED BY SAID FRAME TO OPERATE SAID SWITCH MEANS AT PREDETERMINED POINTS IN THE TRAVEL OF SAID FRAME IN EACH DIRECTION TO REVERSE THE DIRECTION OF TRAVEL OF SAID FRAME AND THE DIRECTION OF ROTATION OF SAID CUTTING CYLINDER. 